Bonding element for friction element assemblies



May 22, 1951. R, E, SPOKES 549%23 BONDING ELEMENT FOR FRICTION ELEMENTASSEMBLIES Filed Sept. 5, 1947 2 Shee'tS-Sheet l grammi@ ay 22, 1951 R.E. sP-OKES y 255mg@ BONDING ELEMENT FOR FRICTION ELEMENT SSEMBLIES FiledSept. 5, 1947 2 Sheets-Sheet 2 Patented May 22, 17951 BONDING ELEMENTFOR FRICTION Y ELEMENT.` ASSEDIBLIES Ray E. Spokes, Ann Arbor, Mich.,assignor to American Brake Shoe Company, Wilmington, Del., a corporationof Delaware Application September 5, 1947, Serial No. 772,316

1 claim. (C1. 117-155) This invention relates to a friction elementassembly comprised of a supporting member such, for example, as an,automotive vehicle brake shoe, and a friction element such as a sectionof brake lining mounted thereon, and to a method of making such afriction element assembly. l v

More particularly, this invention relates to an automotive vehicle brakelining and brake shoe or clutch and clutch facing assembly and to amethod of making such an assembly.

It has been known heretofore that friction elements, lsuch as automotivevehicle brake linings, may be bonded to their supportingv members, suchas the brake shoes of automotive vehicles, by means of suitableadhesives such, for example,

as heat-hardenable or Ythermosetting resins, so

as to avoid the use of fastening elements, such as rivets and the like,and the necessity for boring or drilling the brake shoes and brakelining for the reception of such fastening elements.

Thus, it has been` proposed heretofore, as in United States Patent No.2,272,532, dated February 10, 1942, to William C. Shriver, on BrakeLining Construction, to employ a sheet of resinimpregnated andsupposedly cleavable paper, or like resin-impregnated supposedlycleavable brous material, for vbonding automotive vehicle brake liningto automotive Vehicle brake shoes to the end that when it is desired toreplace the friction elements or, in 'other words, to reline the brakeshoes, the old or used `brake lining could be separated from itsVsupporting member or brake shoe by cleaving or splitting theresinimpregnated paper vbond therebetween.

The practice thus suggested has certain objectionable characteristics,some of which are pointed out in United States Patent No. 2,406,653,granted August 27, 1946, to Clyde S. Batchelor, on Bonded FrictionAssembly. Among these objectionable characteristics are that thesupposed cleavability in the resin-impregnated paper or like fibrousmaterial is, in itself, Vundesirable in that (a) if present in fact itwould impart structural weakness to the resulting assembly; and (b) anyattempt to remove a section of used brake lining by splitting thesupposedly cleavable resin-impregnated bonding paper or like material,as by means of a chisel or the like, is extremely difficult, if notimpossible, and tends to cause damage to the brake shoes or likesupporting members.

In the latter patent referred to above, the patentee endeavored to solvethe problem previously experienced in the art by providingv a bondedfriction assembly in which the intermediate strip of paper or likefibrous bonding material has a thickness within the limits of from0.001..to 0.005".

hesive from penetratingtoo deeply into the paper hydroxide solution.

ness of the paper sheet within the upper limit of 0.005 specified isthat if the paper sheet is substantially thicker than 0.005penetrationof the resin or other bonding adhesive is apt to be insucientwith the result that planes of 'i cleavage may be present in theintermediate or middle Zone of the paper or like fibrous materialbonding sheet with consequent structural Weakness in the resultingcomplete friction assembly..l It has been found in actual practice,however,

that it is very difficult to control the impregnation or penetration ofa thermosetting resin or other heat-hardenable bonding adhesive into asheet of paper having a thickness in the order of 0.001 so that thetendency is for the entire body or thickness of the paper to becomecompletely impregnated with `the resin or other heathardenable bondingadhesive.

move the used brake lining by dissolving out or softening the paperbonding sheet by immersing the complete friction assembly in a strongcaustic solution. The reason for thisv is that since the entire body orthickness of the paper sheet is thus actually impregnated with the resinor otherV heat-hardenable adhesive, it can not be removed by dissolvingit within a strong caustic solution since such a resin-impregnated paperbonding sheet is not substantially attacked vby even a strong causticsolution.

Moreover, it has been found thatl when such .i a friction assembly isimmersed in a caustic solution the only area in which .the causticsolution is effective oneven the unimpregnated portions of the papersheet is along the marginal edges of the paper sheet where the latteris' exposed to and may be attacked by the ycaustic solution.

stili anotherA diniculty whichV presents itsef in attempting to dissolveout or soften the paper 5 AccordingY to such prior practice the 1thickness of the paper or other bonding sheet.V is conned within thelower limit stated, namely,-l 0.001,.to prevent the resin or otherbonding ad- This results in making it very difficult, ifnot impossible,to rebonding sheet in such prior friction element assemblies is the factthat the strong caustic solution tends to develop a high concentrationof semi-dextrinized material where it comes in contact with the paperbonding sheet and this semidextrinized material retards or inhibits thedesired dissolving action of the caustic solution upon theY paperbonding sheet.

It has not been found practical, therefore, to remove used brake lining,or like used friction material, from a friction element assembly byimmersing the complete friction element assembly in a strong causticsolution for the purpose of endeavoring to dissolve out or softenup thepaper or like bonding sheet.

An additional problem which has been encountered in connection withprior attempts to employ resin-impregnated paper or like material forthe purpose of bonding brake lining to a supporting member, such as abrake shoe, and which has not heretofore been successfully solved, isthe problemA of affording suicient thermosetting resin or otherheat-hardenable adhesive at those irregular surface areas between thebrake lining and its supporting shoe which frequently exist is suchfriction element assemblies. This problem is complicated by the factthat if a relatively large and excessive quantity of the thermosettingresin or other heat-hardenable bonding adhesive is employed asubstantial portion of the thermosetting bonding resin or likeheat-hardenable bonding material will exude at the side or marginaledges of the friction element assembly when heat and pressure, areapplied thereto during the bonding operation, and thus form anobjectionable exudate at these points.

Accordingly, an object of the present invention is to afford a new andimproved friction element assembly, and a new and improved method ofmaking the same, which in use overcome the foregoing and other problemsencountered in the use of such friction element assemblies.

-An additional object of the present invention is to afford a novel andeicient method for bonding a friction element, such, or example, as astrip or section of brake lining, to a supporting member such, forexample, as a brake shoe, clutch facingor the like.

A further object of the invention is to provide, as. a new articleofmanufacture, a novel bonding element comprised of a sheet or strip ofpaper or like. fibrous material coated with a novel adhesive. bondingcoatingof the present invention, forv use in bonding a friction elementsuch, for example, as a strip of brake lining, clutch facing, or thelike, to a supporting member such, for ex,- ample, as a brake shoe, orthe like.

Another object of the invention isto provide a novel method of makingthe new bonding element for use in bonding a frictionl element such, forexample, as a strip of brake lining, clutch facing, or the like, to asupporting member such as a brake shoe, or the like.

An additional object of the present invention is to provide a novelbonding composition for use in coating a sheet of paper or like bondingmaterial to a supporting member such, for example, as a brake shoe orthe like.

Other and further objects of the present invention will be apparent fromthe following description and claim and are illustrated in theaccompanying drawings Which, by Way of illustration, show a typicalembodiment of the invention and the principles thereof and what I nowconsider" to be the best mode inwhich I have con- 4 templated applyingthose principles. Other embodiments of the invention embodying the sameor equivalent principles may be used and structural changes may be madeas desired by those skilled in the art without departing from thepresent invention and the purview of the appended claim.

Fig. 1 is a fragmentary top plan View of a section or strip of the newresin-coated bonding paper which forms a part of and is utilized in thepractice of the present invention;

Fig. 2 is an enlarged broken transverse sectional view on line 2-2 inFig. 1;

Fig. 3 is an enlarged fragmentary sectional view of a, friction elementassembly made in accordance with the practice of the present invention;

Fig. 4 is a top plan view of a friction element assembly made inaccordance with the practice of the present invention, a portion of thefriction element or brake lining being broken away to reveal theunderlying and intermediate resincoated paper bonding sheet;

Fig. 5 is a side elevational view of the friction element assemblyillustrated in Figs. 3 and 4; and

Fig. 6 is a transverse sectional view on line 6-6 in Fig. 5.

A friction element assembly made in accordance with the practice of thepresent invention. is illustrated in Figs. 3, to 6 inclusive, of thedrawings, wherein it is generallyindicated at Il), and comprises asupporting member in the form of aA brake shoe I I, a friction elementin the form of a strip of b-rake lining I2, and an intermediateresin-coated bonding strip or member I3 (Figs. 1 and 2). I employ as abase a sheet Illy of suitable absorptive papel or other suitableabsorptive cellulosic material, of suitable thickness, which ispreferably about 0.007". The base sheet I4 may be in the form of a weband I coat and impregnate the base sheet I4 in any suitable manner, asby passing av web of the base sheet I4 through an impregnating andcoating bath having substantially the composition set forth in thefollowing Example l in which all parts indicated are in terms of parts,by weight:

Example 1 Parts by weight Thermosetting phenolic-aldehyde type resin(one-step phenol-formaldehyde resin) 35.5

Asbestos (short fiber) 13.0,

Pigment (cryolite) (NaF)3.A1F3 (pulver=A ized) '7.0

Solvent V(ethyl or denatured alcohol) 19.0

Another suitable impregnating and coating composition which may beemployed in the practice of the present invention, in place of theimpregnatingand coatingcomposition referred to in the foregoing Examplel, is illustrated in the following Example 2, inwhich all partsindicated are by Weight:

ized) 7 Sulphur 0.75 Solvent, monochlorbenzene (20 per cent);

methyl ethyl ketone per cent) 19 in place of the butadiene-acrylonitrilecopolylf; mer referred to in Example 2, above, a like perf centage of achloroprene or chlorinated butadiene eral pigment (cryolite) areintimately mixed lwith the resin-solvent mixture before .the paper basesheet is passed therethrough.'

In the practice of the present invention 1`.0

part of paper, representing 23.0 per cent of the total Weight of thecoated paper base sheet,.was coated with 3.4 parts (77 per cent) .byweight, of the coating and impregnating composition having thecomposition set forth in the foregoing Example 1, or that set forth inExample V2. f

The paper base sheet I4 is thus coated on both surfaces thereof with acoating I5 of asbestos'- flled pigmented thermosettingphenol-formaldehyde resin and, at the same time, a certain amount of theresin penetrates into and impregnates the absorptive paper base sheet I4The thus coated and impregnated paper base sheet I4 is then preferablypassed through or. between pressure or so-called squeeze rolls. Duringthis operation a certain additional amount of the resin is forced intothe body of the paper base sheet I4 and the asbestos-filled andpigmented coating composition disposed upon the surface of the paperbase sheet I4 is caused to assume an irregular or uneven formation,which is indicated at I6 in the drawings and is generally shown in anenlarged scale in Fig. 2. This irregular or uneven formation I6 in thesurface coatings I5 is caused by the tackiness of the asbestos-filledpigmented resin coating and impregnating composition and the resultingdrag or friction of the rubber pressure or so-called squeeze rollsthereon during the operation of passing the thus coated and impregnatedpaper base sheet or web I4I5 therethrough. The thus treated paper basesheet may then be allowed to dry whereupon it is ready for use.

The thermosetting phenol-formaldehyde or equivalent phenolic-aldehyderesin employed in the coating and impregnating bath of the presentinvention is preferably one which has good aging characteristics over awide range of varying condtions of atmospheric temperature and humidityso that the resulting coated and impregnated paper bonding sheet I4-I5will possess good aging characteristics and adequate so-called shelflife when marketed for use by automative vehicle brake service stations,garages, and like places at which the invention may be practiced.

As an alternative procedure and method for use in the practice of thepresent invention, and for preparing the coated and impregnated paperbonding sheet III-I5, a two-step phenol-formaldehyde or equivalentphenolic-aldehyde resin may be employed. In the practice of this form ofthe present invention the paper base sheet or web I4 may be passedthrough an impregnating bath of hexamethylenetetramine, or otherresinhardening agent, whereupon the thus treated paper base sheet or webmay be passed through a bath containing the asbestos-filled andpigmented resin coating and impregnating composition (exclusive of theresin-hardening agent).

The friction element assembly II) is completed by bonding the frictionelement I2, which may be a strip of brake lining, clutch facing or thelike,

ausg-raaf:

toa supporting member such as a brake shoe II by subjecting thecomponent parts of the assembly to heat and pressure in a suitablepress.

In the alternative procedure set forth above the resin-hardening agentwill react with the 4the thermosetting resin component ofi theasbestos-lled and pigmented resin coating and impregnating compositionis fused and the high' areas in the uneven and irregular surface I 64thereof (Fig. 2) are levelled off to form the substantially fiat oruniplanar asbestos-filled and resin-impregnated bonding layers I5 whichare illustrated in Figs. 3 and 6 of the drawings.

When the bonding operation is thus carried out an adequate mass orquantity of the asbestos-V filled and pigmented thermosetting resincoating composition is fused to assure a good bond be-l tween thefriction element or brake lining I2 and its supporting member or brakeshoe I I throughout substantially the entire interfltting surface areabetween the friction element or brake lining I3 and its supportingmember or brake shoe II, including the uneven or irregular surface areaswhich frequently exist in one or both of these parts.

An additional advantage of the above-described method employed in thepractice of the present invention is the fact that due to the asbestosand pigment fillings therein the tendency of the heat-fusible andheat-hardenable or thermosetting resinous adhesive to flow during thebond- 1ng operation is minimized with the result that an excess of thebonding resin is avoided. This eliminates any tendency of the adhesiveresinous bonding compositions to eXude at the sides or marginal edges ofthe friction element assembly during the bonding operation.

Moreover, the asbestos and pigment components of the resinous bondingcomposition employed in the present invention improve the bondingcharacteristics of the resinous bonding composition and of the paperbase sheet I4 coated and impregnated therewith.

In addition, a friction element assembly rmade in accordance with thepractice of the present invention has the further advantage anddesirable characteristics which resides in the fact that the asbestoscomponent of the asbestos-filled and pigmented resin coating andimpregnating composition increases the resistance of the completedfriction element assembly to impacts or shocks to which such frictionelement assemblies are subjected in use.

In the practice of the present invention the used friction element orstrip of brake lining may be removed from its supporting member, such asa. brake shoe, by chiseling the used friction element or brake liningfrom its supporting member or brake shoe, as far as possible, and thengrinding off the remaining portions of the lining and asbestos-filledand pigmented bonding composition to provide a smooth clean surface forthe reception of a new friction element or strip of brake lining.

It will thus be seen from the foregoing description, considered inconjunction with the accompanying drawings, that the present inventionaffords a novel friction element assembly, a novel method of making thenew friction element assembly, and sa novel asbestos-filled andpigmental resin coated and impregnated bonding sheet of 'paper or. likeabsorptivefmaterial for userin making the new friction element assembly.

It will also be seen from the foregoing description, considered inconjunction with the accompanying drawings, that the present inven-jtion has the desirable advantages and charac-- teristics, andaccomplishes its intendedobjects,` including those hereinbeforepointedbut, and others which are inherent in the invention.

I claim: 1

A thermosetting bonding element for use in. bonding a friction elementto a supporting member, the bonding element, composed. of asheet ofabsorptive cellulosic material of the thickness of 0.007 inch, the sheetbeing impregnated with a thermosetting phenolic-aldehyde resin andhaving on both Isides thereof yan uneven coating of, the thermosettingresin, the resin havingr dispersed therein short asbestos fibers andfinely dividedcryolite, the impregnating and.V coating materialconsisting by lweight of about thirty-five. (35) parts of thermosettingresin, thirteen (13) 8, partsV of asbestos fibers and seven (7) parts ofcryolite, the bonding element being composed by weight of about.twenty-eight per cent (28%) cellulo'sic material and seventy-two percent, 5 (72%) impregnating `and coating material.

RAY E. SPOKES.V

REFERENCES CITED The following references are of record in the.l

file of this patent:

UITED STATES PATENTS Tilden Aug. 26, 1947

